Home » HYGIENIC ASSESSMENT OF RADIATION PROTECTION OF PERSONNEL AND RADIATION SAFETY OF PATIENTS DURING USING OF RADIOACTIVE NUCLIDES AND OTHER SOURCES OF IONIZING RADIATION IN PATIENT CARE INSTITUTIONS

HYGIENIC ASSESSMENT OF RADIATION PROTECTION OF PERSONNEL AND RADIATION SAFETY OF PATIENTS DURING USING OF RADIOACTIVE NUCLIDES AND OTHER SOURCES OF IONIZING RADIATION IN PATIENT CARE INSTITUTIONS

June 27, 2024

HYGIENIC ASSESSMENT OF RADIATION PROTECTION OF PERSONNEL AND RADIATION SAFETY OF PATIENTS DURING USING OF RADIOACTIVE NUCLIDES AND OTHER SOURCES OF IONIZING RADIATION IN PATIENT CARE INSTITUTIONS. ORGANIZATION AND SANITARY INSPECTION AT LIQUIDATION OF CONSEQUENCES OF EMERGENCY SITUATIONS FEATURES OF THE TEMPORAL PLACING OF A RESCUE UNITS DURING EMERGENCY SITUATIONS

Naturally occurring ionizing radiation originates both from outside the body, in the form of cosmic radiation and radiation from natural radio-isotopes in the environment, and from inside the body from natural radio-isotopes deposited there from food, drink and air.

During the present century, mankind has been subjected to increasing levels of ionizing radiation from man-made sources, such as X-ray equipment, nuclear weapons, the nuclear fuel cycle, and artificial radioisotopes used for medical and other purposes.

Ionizing radiations may: be divided into two main groups: (1) electrmagnetic radiations (X-ray, and gamma rays), which belong to the same family of electromagnetic radiations as visible light and radio waves; and (2) corpuscular radiations, some of which—alpha particles, beta particles (electrons), and protons—are electrically charged, whereas others (neutrons) have no electric charge.

This distinction between the two groups becomes. blurred, however, when their mode of absorption in materials is considered. The corpuscular types may be regarded as projectiles whose energy is greater than that binding the atoms in chemical compounds. They are therefore capable of breaking chemical bonds and dividing the electrically neutral molecules into positively and negatively charged ions. When X-rays and gamma rays are absorbed, high-energy electrons are released in the irradiated materials, and it is these electrically charged particles–which are similar to the beta particles emitted by radioisotopes—that are the effective ionizing agents. The action of neutrons is more complex. If they collide with the nuclei of hydrogen atoms, these nuclei (or protons) are set in motion, thus producing ionization. Neutrons may also enter atomic nuclei, causing such’instability that the atoms disintegrate and emit radiation that, in turn, produces ionization. Thus the common characteristic of all the types of radiation referred to, whether electromagnetic or corpuscular, is that particles are responsible for the ionization they ultimately produce. Whilst the .exact nature of the biological effects of these radiations is not fully understood, they are related to the ionization that the radiations are capable of producing in living tissue. Thus, the biological effects of all ionizing radiations are essentially similar. However, the distribution of damage throughout the body may be very different according to the type, energy and penetrating power of the radiation involved.

Alpha particles from radioisotopes have ranges of only about 0.001-0.007 cm in soft tissue and less in bone. Beta particles have ranges in soft tissues of the order of several millimetres, i.e., much greater than those of alpha particles in such tissues. A beta particle therefore irradiates many more cells than an alpha particle, but the number of ions produced in each cell is much less.

For X-rays and gamma rays, depending on the energy of the radiation, penetration may amount to tens of centimetres, or even to metres, in soft tissue. As in the case of beta particles, the ion density along the tracks of the electrons ejected by X-rays and gamma rays from the medium through which they pass is much lower than for alpha particles.

NATURAL BACKGROUND RADIATION

This has three components: (1) cosmic radiation originating in outer space and reaching the earth’s surface after reacting with, and being partially absorbed by, the earth’s atmosphere; (2) terrestrial radiation coming from natural radioisotopes present in the earth’s crust; and (3) radiation from natural radioisotopes that have been accumulated in the body as a result of the consumption of food and water and the inhalation of air containing such radioisotopes.

The average values of the dose rates of these three components of environmental radiation lead to a total of about 90 mrad per year to gonodal tissue and bone marrow.

MAN-MADE RADIATION

The evaluation of the radiation exposure of the population presented here applies only to highly developed countries; it refers to the genetic dose’ received by a whole population, rather than to the exposure of individuals or groups. In many countries, the frequency with which radiation is used is much less than in the highly developed countries; the methods applied and the radiation protection measures adopted are, however, sometimes such that the radiation exposure per capita per application is greater. It is impossible, therefore, to give an accurate estimate of the mean genetic dose to the whole world population. The figures quoted will, however, provide an idea of the order of magnitude to be expected.

The contributions to the total dose from man-made radiation will be considered under the following headings:

(1) radiation to patients from the medical uses of radiation;

(2) radiation to occupationally exposed persons;

(3) radiation from “fallout” from nuclear tests;

(4) radiation from other forms of radioactive contamination; and

(5) radiation from radioactive consumer goods and from electronic devices.

Radiation units

It is necessary to distinguish, in considering radiation units, between the following three quantities of importance in radiation protection: exposure, absorbed dose and dose equivalent.

Exposure is the sum of the electrical charges of the ions of one sign produced in unit mass of air under certain defined conditions. The unit of exposure is the Rontgen, which is applicable only to electromagnetic radiation of moderate energy.

The absorbed dose is the radiation energy imparted to unit mass of a specified medium. The unit of absorbed dose is the rad.

For radiation protection considerations, it is necessary to introduce a modified quantity that takes into account the biological effectiveness of a given absorbed dose, depending on the type and energy of the radiation. This is done by using a quality factor. Other factors may also be introduced, such as the distribution factor, which expresses the modification in the biological effect due to the nonuniform distribution of internally deposited radionuclides. The product of the absorbed dose and the modifying factors is termed the dose equivalent. The unit of dose equivalent is the rem. Where the value of the quality factor is close to unity, as is true for X-rays (where it is unity), beta particles, and gamma rays, the numerical values of the absorbed dose in rads and the dose equivalent in rems are practically identical.

BIOLOGICAL EFFECTS OF IONIZING RADIATIONS

Information concerning these effects has been obtained from studies of: (a) patients who have undergone diagnostic or therapeutic procedures with X-rays and radioisotopes; (b) occupationally-exposed persons (for example, pioneer medical radiologists, early workers with radioactive luminous paints, workers, engaged in mining radioactive ores, persons who have been involved in accidents in or around nuclear reactors, and persons who have been exposed continuously to low radiation doses for long periods); and (c) members of general populations who have been affected by atomic bomb explosions or tests of nuclear weapons. This information has been supplemented by evidence from extensive animal experimentation. Despite these studies, there are still many gaps in our knowledge and further investigations are needed. The effects can be regarded as falling into two main groups, namely, somatic effects and genetic effects.

Somatic effects

These effects are observable either relatively soon after individuals have been irradiated (“early” or “short-term” effects), or after periods of a few months to several years (“late” or “long-term” effects). A dose of 1000 rad and above of total body irradiation, delivered over a short period of time, results in death within about a week. Doses of 100-1000 rad of total body irradiation delivered over a short period of time can result in damage and death in a proportion of the individuals exposed.

Acute radiation effects can be observed after irradiation of the greater part of the body. A latent period supervenes after initial symptoms of malaise, loss of appetite and fatigue. The length of this period is roughly inversely proportional to the radiation dose received. The end of the latent period is followed by the onset of the illness: early lethality, destruction of bone marrow, damage to the gastrointestinal tract associated with diarrhoea and haemorrhage, central nervous system symptoms, epilation, dermatitis, sterility. Pathological acute effects arise after exposure to doses hundreds of times greater than those likely to be received from environmental contamination, except in major accidents.

Much less is known as to the effects of small doses, e.g., up to 100 rad, received over long periods of time, yet it is these effects that are particularly importarit for the population at large. There are many uncertainties here—e.g., the variation of sensitivity to radiation with age and the possible reduction in effect per unit of radiation dose as compared with single large doses (over 100 rad).

It is not known whether the linear relationships between radiation dosage and the incidence of harmful effects that are sometimes observed at high dose levels also apply at low dose levels; present estimates of risk from low dose levels are based on the assumption that a linear relationship docs apply and that there is no “threshold” of radiation exposure below which no effect is produced.

At low dosage levels, leukaemogenesis and carcinogenesis are at present accepted as the most serious long-term risks for the individual. There is also evidence, however, of other late effects following high doses, e.g., cataract formation, and possibly neurological damage and a general shortening of the life span. These are all examples of what are called somatic effects.

The frequency of different types of tumour has been found to be increased in irradiated populations. This is true of thyroid carcinomas in patients given X-ray therapy to the neck in childhood, carcinomas of the lung in workers engaged in mining uranium ores, haematite and fluorspar, haemangioendotheliomas of the liver in patients injected intravenously with Thorotrast,’ and miscellaneous types of neoplasms in atomic bomb survivors and in patients subjected to radiotherapy (United Nations Scientific Committee on the Effects of Atomic Radiation, 1972).

An increased incidence of cancers occurred in workers engaged in painting watch and clock dials with luminous paints containing radium. They ingested large quantities of radium and radium daughter elements. These radionuclides, which are preferentially deposited in bone, lead in time to skeletal injury and to osteosarcoma in some victims (United Nations Scientific Committee on the Effects of Atomic Radiation, 1964).

It has only recently been possible to attempt quantitative estimates of the incidence of harmful effects (leukaemia and other forms of cancer and certain genetic effects) per unit dose of radiation, and eveow the margins of uncertainty are very wide. In general, most knowledge has been gained of the effects of relatively large doses received at high intensity, notably from epidemiological studies of the survivors of Hiroshima and Nagasaki and of patients treated with radiation for ankylosing spondylitis and other disorders. Although these estimates are still imprecise, they are adequate to give a rough indication of dose-effect relationship (United States, National Council on Radiation Protection and Measurements, 1971; Upton, 1969).

Leukaemia is the malignancy whose rate of induction per rad is best known, and risk estimates are available over a fairly broad range of doses. For lung cancer and all solid cancers—the incidence of which is also clearly increased by radiation—estimates are much more uncertain, particularly as none of the surveys of irradiated people carried out so far has been pursued for a time sufficiently long to exclude the possibility that further cases of malignancies, besides those already recorded, will be observed after longer periods of observation, and because it is not known whether, some twenty years after exposure, peak incidence has yet been reached.

Despite the lack of direct, quantitative information on the sensitivity of the human embryo to irradiation, it is generally assumed that small amounts of radiation may carry some risk of teratogenic effects in man, as in other species. Thus, to minimize the risk of accidentally irradiating an embryo in a particularly sensitive stage of development, the International Commission on Radiological Protection has recommended that radiological examinations of the lower abdomen and pelvis in a woman of reproductive age should be limited, as far as possible, to the ten days following the onset of menstruation; an undetected pregnancy in such a woman is most improbable at this time (International Commission on Radiological Protection, 1966b).

Because of the paucity of human data on the teratogenic effects of graded doses of radiation and the marked variation in susceptibility of animals to malformation with stage in development at the time of irradiation and with known- species differences, it is not possible to estimate precisely the risks of radiation injury to the human embryo and fetus.

Likewise, studies aimed: at detecting teratogenic effects associated with increased levels of environmental background radiation have -given inconclusive results (Brill & Forgotson, 1964).

Data on human populations on ageing and longevity are incomplete. One of the first indications of life-shortening effects of radiation in man’ was the observation that radiologists in the USA have a higher age-specific death rate than medical specialists in other fields (Dublin & Spiegelman, 1948; Seltser & Sartwell, 1965). This difference implies that occupational irradiation causes a non-specific impairment of health that manifests itself in accelerated ageing. If this interpretation is correct, the lessening of the effect in recent years, during which time there has been increasing attention to radiation safety standards, suggests that the hazard may not be detectable under present working conditions. This is also suggested by the absence of increased mortality in British radiologists (Court Brown & Doll, 1958).

Genetic effects

Genetic effects are the results of gene mutations or chromosome anomalies that, arising in the germ cells of the irradiated individuals, may become apparent in their descendants, sometimes generations removed from the irradiated ancestor. Genetic effects are generally detrimental but may have various degrees of severity, from prenatal death to major malformations or mental dysfunctions, to mild impairments of an individual’s reproductive performance or of his viability. Because they occur among the descendants of irradiated persons, they are of greater concern to the population than to the individuals actually exposed to radiation. Clear evidence of genetic damage in the offspring of irradiated human subjects is so meager that the genetic harm cannot be quantitatively expressed in terms of the social burden to which a given dose of radiation will eventually give rise. However, the possibility that genetic damage, once induced, may persist for generations must be constantly borne in mind when exposing individuals or populations to new sources of radiation (WHO Expert Committee on Radiation, 1959; United Nations Scientific Committee on the Effects of Atomic Radiation, 1966).

Critical organs

For the development of radiation protection guides, the identification of the particular organs or tissues that are critical because of the damage they may suffer is the essential simplifying step. For example, in the case of radioisotopes of iodine, the critical organ is the thyroid, since the concentration of such isotopes in it, and therefore the dose received, is far greater than for any other organ. Since radioiodine is widely used in medicine and may also be of importance iuclear energy, the thyroid may often be the critical organ, especially among children (United States, National Council on Radiation Protection and Measurements, 1971).

In general, for irradiation from internally deposited sources, whether alone or combined with external irradiation, the critical organ is determined more by the metabolic pathways of nuclides, their concentration in organs, and their effective residence times, than by inherent sensitivity factors. Depending on the individual radionuclide under consideration, the critical organ may be the gastrointestinal tract, lung, bone, thyroid, kidney, spleen, pancreas, muscle or fatty tissue.

For general irradiation of the whole body, the critical organs and tissues are the gonads (fertility, hereditary effects), the haematopoietic organs, or more specifically the bone marrow (leukaemia), and the eye (cataracts).

The relation between choice of a critical organ and the development of radiation protection guides is not always evident. The position has been summarized as follows: “The dose to the critical organ from any particular mode of radiation exposure does not define the overall risk which will always be greater than this to the extent to which other organs are irradiated. The concept of critical organ is administratively convenient and in some circumstances logically justifiable, but it does not allow summation of risks according to the relative radiosensitivities of the irradiated tissues” (International Commission on Radiological Protection, 1969b).

Radiation Safety

Once someone decides to include radioactive materials in his/her research, he/she must apply for a radioisotope permit. During the process of obtaining the permit, the radionuclide work procedures will be examined together with other aspects such as the applicant’s training, previous work experience with radioactive materials, adequacy of workplace facilities and preparation, dosimeters used, protective equipment, etc.

As explained earlier, it is better to order radioactive materials only when they are needed or as close as possible to the date of the experiment from both an economic and ALARA perspective. This will also reduce the risks associated with long-term storage, source leakage, external irradiation, etc.

There are three essential methods used to minimize external exposure to radiation in radiation safety: time, distance, and shielding

Time

Reduce the time spend working with radioactive materials as much as possible. A good work practice is to perform the experiment without radioactive material first, to get used to the procedures, and perform the first experiment (if possible) with the smallest amount of radioactive material that will give a readable result. After becoming familiar with the procedures and safe handling of these materials, the quantities used can be increased.

Distance

The second method involves increasing the distance between the body and radioactive materials. Always store radioactive materials and radioactive waste far from other working areas and/or offices. What if the procedure requires working with radioactive materials close to the body? Whenever possible, especially for strong beta and gamma emitters, use tools. Don’t touch the materials with hands unless strictly necessary. However, if hand contact cannot be avoided, manipulation of the materials with gloved hands is required.

Shielding

Most work with radioactive materials at the University will require that the user be quite close to the material. Therefore, working behind shielding is recommended. As explained earlier, different kinds of shielding must be used for different radionuclides. No shielding is required for pure alpha or pure low energy beta emitters. Plexiglass shielding is required for beta emitters, metal for gamma or X-rays, water, and wax or concrete for neutrons. Large enough layers of air, water, or concrete can protect the human body from all types of radiation.

Always check the effectiveness of the shielding before starting an experiment.

http://www.ehs.utoronto.ca/services/radiation/radtraining/module0.htm

Biological Effects of Radiation

There are two types of biological effects of radiation. One is acute, where the amount of damage is proportional to the value of the dose equivalent received by the person. These effects typically relate to high dose levels. This type of biological damage is called a non-stochastic effect of radiation. Sometimes, when controlled, this type of effect may be beneficial to our health. For instance, some forms of cancer therapy utilise high doses of radiation to kill cancerous cells. In our university, large doses causing acute effects are not commonly encountered.

The second types of effects are delayed and statistical (or stochastic) effects. These effects are related to intermediate and low-level doses received by a person. There is no dose-response relationship. The dose relates to a statistical probability of developing a certain effect. The best example is cancer. Exposure to a certain dose can increase the risk of developing cancer. With respect to the foetus, if the dose was received in the first two months of gestation, mental retardation may occur in the offspring.

Radiation is one of the best known carcinogens. Since the last half of the 20th century, our knowledge of this type of cancer has increased dramatically. A statistical proportionality between the level of dose received by a large number of people and the expected effects was proven at a high-to-intermediate level of dose equivalent. Only at much higher doses than those encountered at the University is there a statistical proportionality between cause and effect. A linear extrapolation of this data has been made to low and very low levels of dose equivalent. However, this linear extrapolation method has not been proven scientifically.

Conversely, some studies show that low levels of irradiation are in fact beneficial to our health. However, in the absence of scientific evidence, the regulators adopted a conservative approach and consider all levels of radiation as being damaging to the human body. Because of this, any procedure that involves radioactive materials must abide by a principle called ALARA, keeping all doses ‘As Low As Reasonably Achievable’.

Two types of methods are used to measure external dose. One consists of using instruments such as survey meters, surface contamination meters, and neutron detectors. These instruments comprise the gas filled detectors (Geiger-Müller or proportional detectors), the scintillation detectors, and some special detectors for neutrons.

When performing monitoring the following actions are required:

1. Check first if the right method (direct or indirect monitoring) is required for the type of radionuclide used.

2. Check if the instrument has been calibrated less that a year ago (check the sticker on your instrument) ensure that the battery and HV (when there are available) indicators are in the correct range.

3. Measure the background before reading the values in the work area.

4. Subtract the background after taking readings in the work area.

5. With the remaining number and the instrument’s efficiency for that particular radionuclide (see sticker), estimate the level of contamination.

6. Take the necessary actions to reduce the contamination below the set limits.

The second method for measuring external dose is personal dosimetry.

Biological Effects

The occurrence of particular health effects from exposure to ionizing radiation is a complicated function of numerous factors including:

· Type of radiation involved. All kinds of ionizing radiation can produce health effects. The main difference in the ability of alpha and beta particles and Gamma and X-rays to cause health effects is the amount of energy they have. Their energy determines how far they can penetrate into tissue and how much energy they are able to transmit directly or indirectly to tissues.

· Size of dose received. The higher the dose of radiation received, the higher the likelihood of health effects.

· Rate the dose is received. Tissue can receive larger dosages over a period of time. If the dosage occurs over a number of days or weeks, the results are ofteot as serious if a similar dose was received in a matter of minutes.

· Part of the body exposed. Extremities such as the hands or feet are able to receive a greater amount of radiation with less resulting damage than blood forming organs housed in the torso. See radiosensitivity page for more information.

· The age of the individual. As a person ages, cell division slows and the body is less sensitive to the effects of ionizing radiation. Once cell division has slowed, the effects of radiation are somewhat less damaging than when cells were rapidly dividing.

· Biological differences. Some individuals are more sensitive to the effects of radiation than others. Studies have not been able to conclusively determine the differences.

The effects of ionizing radiation upon humans are often broadly classified as being either stochastic or nonstochastic. These two terms are discussed more in the next few pages.

http://ess.geology.ufl.edu/ess/Notes/040-Sun/primer.html

Exposure Limits

As discussed in the introduction, concern over the biological effect of ionizing radiation began shortly after the discovery of X-rays in 1895. Over the years, numerous recommendations regarding occupational exposure limits have been developed by the International Commission on Radiological Protection (ICRP) and other radiation protection groups. In general, the guidelines established for radiation exposure have had two principle objectives: 1) to prevent acute exposure; and 2) to limit chronic exposure to “acceptable” levels.

Current guidelines are based on the conservative assumption that there is no safe level of exposure. In other words, even the smallest exposure has some probability of causing a stochastic effect, such as cancer. This assumption has led to the general philosophy of not only keeping exposures below recommended levels or regulation limits but also maintaining all exposure “as low as reasonable achievable” (ALARA). ALARA is a basic requirement of current radiation safety practices. It means that every reasonable effort must be made to keep the dose to workers and the public as far below the required limits as possible.

Regulatory Limits for Occupational Exposure

Many of the recommendations from the ICRP and other groups have been incorporated into the regulatory requirements of countries around the world. In the United States, annual radiation exposure limits are found in Title 10, part 20 of the Code of Federal Regulations, and in equivalent state regulations. For industrial radiographers who generally are not concerned with an intake of radioactive material, the Code sets the annual limit of exposure at the following:

1) the more limiting of:

· A total effective dose equivalent of 5 rems (0.05 Sv) or The sum of the deep-dose equivalent to any individual organ or tissue other than the lens of the eye being equal to 50 rems (0.5 Sv).

2) The annual limits to the lens of the eye, to the skin, and to the extremities, which are:

· A lens dose equivalent of 15 rems (0.15 Sv)

· A shallow-dose equivalent of 50 rems (0.50 Sv) to the skin or to any extremity.

The shallow-dose equivalent is the external dose to the skin of the whole-body or extremities from an external source of ionizing radiation. This value is the dose equivalent at a tissue depth of 0.007 cm averaged over and area of 10 cm².
The lens dose equivalent is the dose equivalent to the lens of the eye from an external source of ionizing radiation. This value is the dose equivalent at a tissue depth of 0.3 cm.

The deep-dose equivalent is the whole-body dose from an external source of ionizing radiation. This value is the dose equivalent at a tissue depth of 1 cm.

The total effective dose equivalent is the dose equivalent to the whole-body.

The three basic ways of controlling exposure to harmful radiation are: 1) limiting the time spent near a source of radiation, 2) increasing the distance away from the source, 3) and using shielding to stop or reduce the level of radiation.

Time
The radiation dose is directly proportional to the time spent in the radiation. Therefore, a person should not stay near a source of radiation any longer than necessary. If a survey meter reads 4 mR/h at a particular location, a total dose of 4mr will be received if a person remains at that location for one hour. In a two hour span of time, a dose of 8 mR would be received. The following equation can be used to make a simple calculation to determine the dose that will be or has been received in a radiation area.

Dose = Dose Rate x Time

(click here for more information on using this formula)

When using a gamma camera, it is important to get the source from the shielded camera to the collimator as quickly as possible to limit the time of exposure to the unshielded source. Devices that shield radiation in some directions but allow it pass in one or more other directions are known as collimators. This is illustrated in the images at the bottom of this page.

Distance
Increasing distance from the source of radiation will reduce the amount of radiation received. As radiation travels from the source, it spreads out becoming less intense. This is analogous to standing near a fire. The closer a person stands to the fire, the more intense the heat feels from the fire. This phenomenon can be expressed by an equation known as the inverse square law, which states that as the radiation travels out from the source, the dosage decreases inversely with the square of the distance.

Inverse Square Law: I₁/ I₂ = D₂²/ D₁²

(click here for more information on using this formula)

Shielding
The third way to reduce exposure to radiation is to place something between the radiographer and the source of radiation. In general, the denser the material the more shielding it will provide. The most effective shielding is provided by depleted uranium metal. It is used primarily in gamma ray cameras like the one shown below. The circle of dark material in the plastic see-through camera (below right) would actually be a sphere of depleted uranium in a real gamma ray camera. Depleted uranium and other heavy metals, like tungsten, are very effective in shielding radiation because their tightly packed atoms make it hard for radiation to move through the material without interacting with the atoms. Lead and concrete are the most commonly used radiation shielding materials primarily because they are easy to work with and are readily available materials. Concrete is commonly used in the construction of radiation vaults. Some vaults will also be lined with lead sheeting to help reduce the radiation to acceptable levels on the outside.

Radiation protection of personnel and radiation safety of patients during X-ray procedures.

Amongst sources of ionizing radiations, used in medical departments, the most common are X-ray diagnostic apparatuses. X-ray radiation, generated by those apparatuses, is characterized by significant penetrating power and, as a result, may pose hazard for personnel of X-ray subdivisions, patients, undergoing radiological procedures, persons that are in adjacent premises and on adjacent territory. That is why their allocation, planning and exploitation must satisfy the requirements of radiation safety.

Requirements to allocation, planning, arrangement, sanitary and technical equipment of radiological subdivisions of hospitals, radiation protection of their personnel and radiation safety of patients are stated in «Building rules and norms», «Sanitary rules and norms – X-ray departments (rooms)» (SRandN 42–129–11–4090–86), «Sanitary rules of work during medical X-ray procedures» (№ 2780–80).

Sanitary legislation does not permit allocation of radiological departments (rooms) in residential houses and child’s institutions. No particular requirements to their allocation in patient care institutions are in place. But with the purpose of decrease of amount of adjacent premises for permanent sojourn of personnel and patients, advantage has been given to block-type arrangement in separate outhouse or on the ground or on the last floor of buildings.

Main premises of X-ray room is the treatment room – it is the premises, where X-ray apparatuses are located and all kinds of X-ray procedures are conducted. Existing legislation forbids their allocation under (over) wards for pregnant or children or in adjacent with them premises.

Radiation protection of adjacent territory (in case of location of X-ray room on the ground floor) and adjacent premises is provided by shielding by building structures (walls, overlappings, partitions), material and thickness of which must decrease radiation intensity to allowable level.

Weak spots in radiation protection by using building structures are doors and windows. Elimination of this defect is achieved by covering of doors by iron, leaden or lead-impregnated rubber plates; equipping windows with iron shutters (wooden with covering of iron or lead-impregnated rubber) or by raising of window-sill to 1.6 m height above floor-level.

Area of treatment room is regulated with purpose of protection of adjacent premises and it must be no less than 34 m² for every X-ray apparatus, which must be located such way, that the distance between focus of X-ray tube and walls would not be less than 2 m and its radiation would be directed mostly in direction of main wall. Area of treatment room is enlarged by 15 m² for every extra X-ray apparatus. X-ray tube is located in flask with collimator that forms work beam.

Protection of radiologist is provided by:

– lead-impregnated glass that covers fluorescent screen;

– multiple-stripe apron of lead impregnated rubber, that is hung onto screening device;

– small protective screen;use of individual safety means (gauntlet, apron from lead impregnated rubber (in textile cover for protection from diffusion of lead)) in special cases.

Protection of laboratory assistant of X-ray room is provided by allocation of his work place in separate adjacent premise that is called control room (panel room). This work place is provided with window of lead-impregnated glass to treatment room and with means of direct communication with doctor.

In addition to treatment room and panel room, planning of X-ray room or X-ray department must have:

– consulting room – 10 m²;

– photographic laboratory – 6 m²;

– booth for preparation of barium solutions – 4 m²;

– cloakroom – 2.5m²;

– toilet;

– waiting room (in polyclinic).

Sojourn of paramedical personnel in treatment room or panel room during radiological procedures is not allowed.

During radiological examinations persons that take part in them – personnel of other departments of hospital, alliance of patient, attendants that have to support child or infirm may stay in treatment room in conditions that dose received by them does not exceed level of irradiation of category B.

Radiation safety of patients is based on decrease of radiation exposure during X-ray examination of population especially pregnant, children and adolescent that can be achieved by complex of organizational, medical and technical measures. Organizational measures provide regulation of X-ray examination of population, restriction of annual dose of irradiation for different categories of patients, raising the level of personnel’s skill and responsibility for performance of procedures.

They are given in order, sanitary regulations, methodical instructions by Ministry of Public Health of Ukraine. All patients that are subject to X-ray examination according to their destination are divided into four categories.

Category A_d– patients with diagnosed or suspected oncological diseases, patients, examinations of which is conducted with purpose of differential diagnosis of congenital cardiovascular pathology, patients that get radiotherapy, patients that are examined on living indications in urgent practice. Recommended limit of annual irradiation for persons of this category is 100 mSv.

Category B_d – patients, examination of which is conducted on clinical indications at non-oncological diseases with purpose of specification of diagnose and (or) selection of treatment tactics. Recommended limit of annual irradiation for persons of that category is 20 mSv.

Category C_d – persons from risk groups including workers of enterprises with harmful conditions of work and those that pass through occupational selection for work at such enterprises, patients that are taken off the books after curative treatment of oncological diseases. Recommended limit of annual irradiation for persons of that category is 2 mSv.

Category D_d – persons that pass through all kinds of prophylactic examinations except those referred to category C_d. Recommended limit level of annual irradiation for persons of that category is 1 mSv.

Medical measures include: selection of method of examination, restriction of irradiation area to minimum values necessary for arrangement of diagnose of disease, protection of surrounding tissues by shields of lead-impregnated rubber, right selection of pose at roentgenography. Such shields (and apron of radiologist) are to be in textile covers for protection from diffusion of lead.

For decrease of gonadal dose during X-ray examination of organs of abdominal cavity, lumbosacral part of vertebral column and other organs shielding of gonads is foreseen.

Different ways of improving of X-ray image: production and use of fast X-ray films, right selection of operating mode of X-ray apparatus (conducting of examinations at minimum values of anode current and voltage on X-ray tube), use of electro-optical image amplifier that permit to get more sharp and brilliant image at dose-sparing regimen of work of apparatus, use of wide-screen Roentgenofluorography during prophylactic examinations are referred to technical measures that provide decrease of radiation exposure.

Maintenance of dark adaptation of sight of radiologist during X-ray examinations has high profile.

Channels of exhaust ventilation in treatment room must be located in upper part of premises – for removal of ionized by high voltage air and in lower part (under floor) – for removal of leaden dust.

Radiation protection of personnel and radiation safety of patients in radiological departments of hospitals

Different quantum and corpuscular irradiations are used for radiotherapy. Their sources are:

– β-, γ- radiating radioactive nuclides in a form of bare and sealed sources;

– X-ray apparatuses that are generators of quantum radiation of low and middle energies;

– betatrons and linear accelerators that generate inhibitory and corpuscular irradiations of high energies.

Existent ways of radiotherapy are divided into two basic parts: 1) ways of teleirradiation; 2) ways of contact irradiation.

In case of teleirradiation source is located at considerable distance from patient (long-distance irradiation) or at insignificant distance (short-distance irradiation). In both cases, beam of radiation is giveecessary width and shape and directed onto region that is subject to irradiation.

Contact irradiation includes: application way, when sealed sources are located on body surface that is irradiated by special devices – masks, applicators; intracavitary – when source of radiation is introduced into one of body cavities and intraorganic – when source of radiation is introduced directly into tissue of tumour.

Variety of ways and methods of radiotherapy is determined by necessity of fulfillment of basic principle of radiotherapy – concentration of radiation energy in abnormally changed tissues, combined with maximum decrease of dose in surrounding tissues and the whole body.

Radiation hazard for personnel of radiological departments, patients that receive radiotherapy, persons that can be in different premises and on territory that is adjacent to building depends on the way of radiotherapy and technical ways for its conduction.

Because of that, a number of requirements, stated in «Building rules and norms» and «Rules on work with radionuclides in establishments of Ministry of Public Health» are made for allocation of radiological departments of hospitals, organization of radiation protection of personnel and radiation safety of patients and population.

Radiological departments of hospitals are usually located in one-storey buildings with asymmetric-block planning that provides isolated location of every organization department:

– department of teletherapy;

– department for treatment by sealed sources;

– department for treatment by bare sources;

– department (laboratory) of radioactive nuclide diagnostic.

Department of teletherapy

Basic organization units of this department are treatment rooms with control rooms.

The following devices are used for teletherapy:

– roentgenotherapy units that generate radiation with energy 0.1 – 0.3 MeV;

– betatrons that generate electronic radiation with energy 15 – 30 MeV;

– γ-therapeutic unit with activity of radioactive nuclide (cobalt-60) from 1 200 to 6 000 Curie and energy of γ-radiation 1.17 and 1.33 MeV.

Teleirradiation can be static and mobile. In case of static irradiation, source of radiation during session of irradiation is in fixed position relative to patient, mobile irradiation is characterized by removal of source in relation to patient in the process of irradiation, that can be rotary, sectored and tangent.

Radiation hazard in department of teletherapy is characterized by possibility of only external irradiation of personnel and patients.

Radiation protection of adjacent premises and territory that is adjacent to block of teletherapy is provided by:

– building structures of lead with wall thickness more than 1 m;

– organization of treatment rooms without daylight;

– rational formation of beam of radiation, generated by source with help of different devices – apertures, filters, collimators to put it into certain measures and shapes for maximum decrease of penetrability in adjacent premises;

– equipping of unavailability zone on adjacent territory.

Radiation protection of personnel is provided by:

– sojourn of personnel in control room (protection by shielding);

– application of technical ways of observation and language contact with patients during procedures;

– equipping the labyrinth-like entrance into the treatment room;

– regulations of continuance of working day (protection by time).

Radiation safety of patients is provided by:

– rational selection of way of irradiation;

– rational formation of beam of radiation in order to decrease possibility of deleterious effects on healthy tissues.

Department for treatment by sealed sources

Contact methods of irradiation (application, intracavitary, interstitial) when sources of irradiation in form of radionuclide preparations are located in direct contact with surface of pathologic process or are introduced right into tumour, are used in this department.

Sealed sources are radioactive nuclides, physical state of which (metal), or envelope they are in prevent the possibility of pollution of environment with them (including tissues of patient). In most cases sealed sources have shape of cylinders with noses or needles with rounded and sharpened ends, short shanks, small balls that contain γ- radiating radioactive nuclides – cobalt-60, cesium-137, tantalum-182, iridium-192 or β-radiating radioactive nuclides – phosphorus-32, strontium-90, yttrium-90, promethium-147, thallium-204.

In case of application method of irradiation, special fixing device (colpostat, endostat) must be introduced into cavity and the source of irradiation only after that. Then the source of irradiation can be installed without participation of medical personnel by programmed automatic systems or by unmanned manipulators.

Basic structural units of department for treatment by sealed sources are block of radionuclide security, that contains: depository of sources of irradiation, treatment room, manipulation room, radiological wards, domestic and other premises.

Radiation hazard in this department is characterized by possibility of external irradiation only.

Radiation protection of adjacent premises and territory is provided by:

– usual building structure, thickness of which must correspond to requirements of existing legislation;

– regulation of summary activity of radionuclide sources in radiological wards;

– equipping of zone of unavailability on adjacent territory.

Radiation protection of personnel is provided by:

– use of all ways of radiation protection (protection by distance, by time, by amount, by shields (all manipulations with sources must be conducted only in protective housing and behind shields, entrance in manipulation room must have protective wall of concrete from inside));

– maintenance of regulations on radiation safety and sanitary regulations during work with sources of irradiation.

Radiation safety of patients is provided by:

– rational selection of way of irradiation;

– maintenance of existing rules of conduction of radiotherapy.

Department for treatment by bare sources

Bare sources are radioactive nuclides, during work with which the pollution of environment – air, hands, clothes, other surfaces is possible. Open sources are β-, γ- radiating substances in powder–like form and in form of true solutions, colloidal solutions, suspensions that are introduced in tumours through injection needles. Radioactive nuclides of iodine are introduced into organism by alimentary tract.

Department of treatment by bare sources contains:

– block of radionuclide security that contains: depository of sources of irradiation, filling room, treatment room, washing room, rooms of temporarily storing of radioactive waste, settling bowls of collecting system;

– radiological wards;

– sanitary and domestic premises.

Radiation hazard in department for treatment by bare sources is characterized by possibility of external and internal irradiation of personnel, possibility of ejection of radioactive nuclides behind the borders of department.

In this connection, special requirements are made to equipping of premises of block of radionuclide provision, radiological wards, water-supply, sewerage, sanitary and domestic premises, operating mode, rules of personal hygiene, working clothes, special air discharge purification systems, filtering of air.

Character of those requirements depends on class of work with radioactive nuclides.

According to MASRU–01 all works with bare sources are divided into 3 classes. Class of work depends on two conditions:

– groups of radiation hazard, to which radioactive nuclide belongs (MSRU–01 all radioactive nuclides depending on possible radiation hazard, made by them are divided into 4 groups: group A – radioactive nuclides with particularly high radiation hazard; group B – radioactive nuclides with high radiation hazard; group C – radioactive nuclides with moderate radiation hazard; group D – radioactive nuclides with small radiation hazard);

– activity of radioactive nuclide at the workplace.

Radiation protection of personnel is provided by:

– use of all ways of protection from external irradiation;

– maintenance of requirements of radiation asepsis, that prevent possibility of internal irradiation;

– maintenance of rules of personal hygiene. Radiation safety of patients is provided by maintenance of requirements of radiation asepsis inside the department.

Finally it has to be marked that all methods of protection from ionizing radiation (by amount, by distance, by time, by shield) can be divided into legislative (normative) and organizational and technical.

Protection by amount is legislatively regulated by NRSU-97(dose limit, allowable levels of entrance of radioactive nuclides into organism by inhalation, alimentary track, allowable concentrations of radioactive nuclides in the air, drinking water, allowable levels of pollution by radioactive nuclides of working surfaces, clothes, hands of personnel, regulated activities of radioactive nuclides at workplaces and other).

Protection by time is legislatively regulated by decrease of working time of personnel (category A), increase of continuance of leave and more earlier retiring on a pension.

Protection by distance and shielding is provided legislatively by construction regulations; rules that provide for proper standards of area, capacity of corresponding premises, their technical equipment and others.

Scheme of sanitary inspection of radiological department of hospital

1. Name and address of hospital or polyclinic, allocation of rooms (building, floor, adjacent premises).

2. Presence and condition of paper maintenance (journal of dosimetry, instructions etc.).

3. Planning of rooms (list of rooms, their area).

4. Type of X-ray apparatus, voltage and current strength in tube.

5. Destination of X-ray apparatus (diagnostic, therapeutical, photofluorographic, defectographic). Immovable, unidirectional, various directional working beam.

6. Presence and type of ventilation in treatment room, upper and lower exhaust ducts. Natural and artificial lighting.

7. Protection from X-ray radiation of work places of radiologist, X-ray technician and adjacent premises (protective screens, lead-impregnated glass, walls, windows, individual safety methods). Calculations of effectiveness of their protection.

8. Presence and type of Ionometers, personal dosimeters, their logbooks, dates of examinations.

9. Degree of preparation of personnel (special education, improvement).

Scheme of hygienic estimation of radiation protection in radiological department of hospital

1. General characteristic of radiological department of hospital.

Name of patient care institution, its departmental submission, address.

Characteristic and assessment of allocation of building of radiological department on the area, type of building, presence of zone of unavailability, presence of control area, its measures.

Structure of department, peculiarities of allocation and planning of its subdivisions, functional connection between them.

Assessment of radiation environment on territory of control zone and outside of it by determination of absorbed dose rate in the air of γ-radiation and radioactive pollution of soil.

2. Department of teletherapy.

Allocation and planning of department, basic premises, characteristic of devices used for radiotherapy.

Radiation protection of control room, adjacent premises and territory from γ-radiation (presence of protective shroud on radiating device, materials and thickness of walls in treatment room, presence of protective labyrinth at entrance, protective doors, their freeze, presence of attentive light alarm).

Observing system for irradiation of patients.

Characteristic and assessment of ways of protection of patients from accessory irradiation.

Assessment of effectiveness of radiation protection in control room and other adjacent premises by calculation method and measurement of absorbed dose rate in the air.

3. Departments for treatment by sealed sources.

Allocation and planning of department.

Sources of irradiation that used in department, their activity, methods of application of sources to patients (manual-linear and consistent).

Characteristic of radiation dangerous premises (depository for sources of irradiation, radiomanipulation room, radiotreatment room), their accordance to hygienic requirements.

Conditions of storage and transportation of sources of irradiation.

Ways of radiation protection of personnel in depository for sources of irradiation, radiomanipulation room, radiotreatment room.

Radiation protection of adjacent premises and territory.

Assessment of effectiveness of radiation protection by necessary calculations and measurement of absorbed dose rate in the air of workplace, behind shields, in adjacent premises, on adjacent territory.

4. Department for treatment by open sources.

Allocation of department, characteristic of use of radioactive nuclides, class of radiation hazard it belongs to.

Characteristic of radiation dangerous premises (depository of radioactive nuclides, filling room, treatment room, washing room, radiological wards) their accordance to permitted class of works, sanitary improvement (covering of walls, floor, exhaust hoods, ventilation, collection, removal and sterilization of solid and liquid radioactive waste).

Presence of means of radiation protection: protective shields, boxes, remote instruments.

Presence of individual radiation protection devices for personnel: working clothes, overalls, aprons, arm-bands, breathing masks and others.

Sanitary and domestic premises for personnel.

Results of measurements and assessment of level of radioactive pollution of workrooms and other premises.

5. Acquaintance with documentations of radiological department, its types.

Analysis and assessment of materials of radiological and medical control during previous year and current year.

6. Conclusions.

Training instruction on calculation of parameters of protection from external γ-radiation based on weekly doses of radiation, expressed in roentgens

For assessment of labour conditions during work with sources of γ-radiation and for calculation of protection from external radiation, formulas (1), (2), are used, which indicate dependence of radiation dose (D) from amount of radioactive nuclide (activity of source), time of radiation and distance between source of radiation and exposed object:

(1)

(2)

where: Q – activity of the source in milliCurie;

M – activity of source in mg/equv. of Radium;

K_γ – γ-coefficient of radioactive nuclide (table 1);

8.4 – γ-coefficient of Radium;

t – time of radiation during workweek – in hours(30 hours at roentgenologist and radiologist at work with sealed sources; 27 hours – at work with bare sources);

R – distance between source and exposed object in centimeter.

Assessment of labour conditions is carried out by comparing calculated dose with allowable level for category A – 20 mSv per 50 workweeks = 0.4 mSv/week that is equal to 0.04 roentgens per week for γ- radiation.

Transforming the above-mentioned formula regarding Q or M, t or R, activity, time or distance, that provides safety for the personnel, can be determined. In transformed formula dose of radiation is indicated as D₀ and it corresponds to allowable dose during workweek – 0.04 roentgens (0.4 mSv).

In case of protection by amount, by distance or by time, does not provide radiation safety, shields are used.

For determination of thickness of shield, damping has to be found – the number that shows how many times with shield’s help, radiation must be decreased in order to receive dose of radiation that would not exceed allowable limit. Damping is found by formula (3)

(3)

where: D – is calculated real dose of radiation for certain labour conditions;

D₀ – allowable dose of radiation.

On basement of damping and energy of γ- radiation of given radioactive nuclide (that is given in table 1) in special tables (look at table 3, 4, 5) thickness of shield, made of corresponding material – lead, iron, concrete is found.

Training instruction on calculation of parameters of protection from external γ-radiation based on determination of absorbed dose rates in the air, expressed in microGray per hour

For assessment of effectiveness of radiation protection during work with sources of gamma-radiation and calculation of its parameters, you are to have such data on radiation conditions:

– activity of source of gamma-radiation in Becquerel (Bq);

– energy of gamma-radiation in mega-electronvolt (MeV);

– distance between source of radiation and object of irradiation in meters (m);

– time of radiation in hours (hour);

– kerma of radioactive nuclide;

– absorbed dose rate in the air in microGray per hour, (μGy/hour);

– material for protection (its name and density).

Assessment of accordance of parameters of radiation protection to requirements of existing legislation is based on comparison of calculated absorbed dose rate in the air (AD) with permissible absorbed dose rate in the air (PAD).

Amount of absorbed dose of external radiation rate in the air is calculated according to the following formula:

Р = , (4)

where: P – is absorbed dose rate in the air Gy/hour (calculated by this formula absorbed dose rate in the air is expressed in Gy/hour, for recalculation it in μGy/hour it has to be multiplied by 10^-6);

A – activity of the source of γ-radiation in Becquerel (Bq);

G – kerma of radioactive nuclide – summary initial kinetic energy of all charged particles, framed by influence of secondary ionizing radiation. Systemic unit of kerma is Gray, off-system unit is rad. Value of kerma is found in special table or is counted by multiplying gamma coefficient of radioactive nuclide by coefficient – 6,.5 and γ-coefficient is found in table 1 («Physical characteristics of radioactive nuclides»);

t – time of irradiation in seconds (if that time is given in hours than it has to be multiplied by 3600 for recalculation of time expressed in seconds);

R – distance between source of radiation and exposed object in meters (m).

Similarly to calculations by formulas (1) and (2), transforming formula (4) relatively to A, t or R, or parameters of protection by amount (activity), by distance or by time can be detected at necessity.

At the same time dose rate in transformed formulas is indicated as P₀ has to be suited to amount of allowable absorbed dose rate in the air (see table 6).

Calculation of protection from external γ-radiation by shields is carried out similarly to indicated above sample.

First stage of calculation of protection by shield is calculation of absorbed dose rate in the air from certain source according to given above formula.

Second stage of calculation is determination of necessary damping of absorbed dose rate in the air. Formula (5) is used for that:

К = (5)

where: K – damping factor;

P – calculated actual absorbed dose rate in the air;

P₀ – permissible absorbed dose rate in the air (see table 6).

Third stage is determination of thickness of shield from suitable material (lead, iron, concrete) by quantity of necessary damping of γ-radiation and its energy. The same tables 3, 4, 5 are used for that purpose.

Table 6

Permissible absorbed dose of gamma-radiation rates in the air that are used for planning of protection from external irradiation

Categories of

exposed person

Destination of premises and territories

Continuance of irradiation hour/year

Permissible absorbed dose rate in the air mcSv/hour

Personnel

Persons of category A

Premises of permanent stay of the personnel

1 700

6.0

Premises of sojournment stay of the personnel

850

12.0

Persons of category B

Premises and territory of object where persons that refer to category B are

2 000

1.2

Persons of category C

Other premises and territory

8 800

0.06

Comment: Values of AD are given with double safety factor that is caused by peculiarities of planning of protection.

Training instruction on method of calculation of thickness of protector from X-ray radiation

Calculation of thickness of walls, floor, and ceilings of premises of X-ray room, protective screens and shields consists of three operations:

– determination of necessary damping factor of X-ray radiation (K) that shows how many times dose rate has to be decreased to permissible;

– determination of thickness of protection by lead that is necessary for decrease of absorbed dose rate in the air that was produced by source of X-ray radiation to allowable level;

– recalculation of founded thickness of protection by lead to material which planned or existing constructions are made of.

Formula (6) is used for calculation of damping of X-ray radiation during determination of dose rate in the air in roentgens per hour:

(6)

where : I_st – standard anode current of X-ray tube (1-3 mA);

R – distance between X-ray tube and place of protection, m;

PDR – permissible absorbed dose rate in the air (exposure dose) of radiation, mR/hour (see table 7).

Table 7

Permissible dose rate in roentgenologic departments and X-ray room, mR/hour

Kind of premises

planned

existing

Premises for permanent stay of the personnel (treatment room, panel room)

1.7

3.4

Premises of sojournment of the personnel and adjacent premises

0.12

0.24

Wards for patients

0.03

0.06

Necessary thickness of protection by lead depending on damping and voltage on X-ray tube are to be found in special table (see table 8).

Thickness of protection by building materials are to be found by their leaden equivalents in table 9.

Training instruction on calculation of protection from X-ray radiation at determination dose rates in μGy/hour

Calculation of protection from X-ray radiation by shielding is based on determination of damping of absorbed dose of X-ray radiation rate in the air (DR) at absence of protection to permissible level of absorbed dose rate in the air (PDR) at the same spot of the premises due to shield. These calculations are in roentgens per hour at expression of dose rates in μGy/hour.

Stationary ways of radiation protection of treatment room and X-ray room (walls, ceiling, floor, doors, watch window between treatment room and panel room) are to provide damping of X-ray radiation to such level when absorbed dose rate in the air at work places of the personnel, in adjacent rooms and on the territory that borders upon treatment room at location of X-ray room on the ground floor, will not exceed absorbed dose rate.

Damping of X-ray radiation (K) is calculated by formula (7):

(7)

where: DR – is calculated actual absorbed dose of X-ray radiation rate in controlled spot, mGy/hour;

PDR – is permissible absorbed dose rate in the air by means of permanent protection, μGy/hour. (see table 10);

10³ – is coefficient for recalculation of absorbed dose rate in the air, expressed in mGy on dose rate expressed in μGy;

H – radiation outlet is absorbed dose rate in the air in initial beam of X-ray radiation at 1 meter distance from focal spot of X-ray apparatus mGy×m²/mA×min. Value of this radiation outlet is found in log of X-ray apparatus or in table (see table 11);

W – working load (anode current) of X-ray apparatus (mA×min) per week. It is calculated based on regulated continuance of carrying out of radiological data at standard values of anode current. These data are given according to type and destination of X-ray apparatus in table 12.

N – coefficient of directivity of radiation. In X-ray apparatus this coefficient is equal to 1, in apparatus with mobile source of radiation (X-ray computed tomographic scanner, panoramic tomographic scanner) coefficient of directivity is 0.1 and in directions where only scattered radiation hits – 0.05.

30 – value of regulated time of work of X-ray apparatus during week (hour/week);

r – distance between focus of X-ray tube and place of measurement of radiation level in meters is determined by project documentation of X-ray room.

Table 10

Permissible absorbed dose rate of X-ray radiation (PDR) at permanent protection of treatment room of X-ray room

Premises, territory

PDR,

μGy/g

LD,

mSv/year

Premises of permanent stay of the personnel of category A (treatment room, panel room, room for preparation of barium meal, photographic darkroom, consulting room)

13.0

20.0

Adjacent premises to treatment room of X-ray room in horizontal and vertical directions that have places of permanent stay of personnel of category B

2.5

5.0

Adjacent premises to treatment room of X-ray room in horizontal and vertical directions without permanent work places (entrance hall, checkroom, footsteps, corridor, rest room, toilet, stockroom and others)

10.0

5.0

Premises of occasional stay of the personnel of category B (technical floor, cellar, attic etc.)

40.0

5.0

Wards of hospital adjacent in horizontal and vertical directions with treatment room of X-ray room

1.3

1.0

Adjacent territory to external walls of treatment room

2.8

1.0

Adjacent quarter to treatment room of radiodontics

0.3

1.0

Table 11

Value of radioactive outlet H at 1 m distance from focus of X-ray tube (anode current is constant, anode current rate is 1 mA, additional filter 2 mm AI for 250 kV-0.5mm Cu)

Anode current, kV

100

150

200

250

Radioactive outlet,

mGy×m² (mA×min)

6,3

Table 12

Standard values of working load W and anode current U during calculation of permanent protection

№

X-ray equipment

Working load, (mA×min)/week

Anode

current, kV

Roentgenofluorography apparatus without shielded box

4 000

100

Roentgenofluorography apparatus with shielded box, numerical photoroentgenograph, X-ray examination apparatus with digital image processing

2 000

100

X-ray examination complex with full set of tripods

1 000

100

X-ray apparatus for radioscopy

(first workplace – rotary table-tripod – RTT)

– in horizontal position of RTT

– in vertical position of RTT

800

100

200

100

X-ray apparatus for radiography

(2 and 3 workplaces – table of roentgenogram)

1 000

100

Angiography complex

1 000

100

CT-scanner

400

125

Surgical moving apparatus with X-ray image amplifier

200

100

Ward X-ray apparatus

200

Roentgenourology table

400

X-ray apparatus for lithotripsy

200

Mammographic X-ray apparatus

200

X-ray apparatus for programming of radiotherapy (simulator)

200

100

Apparatus for short-focus roentgenotherapy

5 000

100

Apparatus for long-focus roentgenotherapy

12 000

250

Osteodensitometer for whole body

200

rated

Osteodensitometer for limbs

100

Calculation of protection is normally carried out at following locations:

– right up to internal surface of walls of the premises that border upon treatment room of X-ray room or external walls;

– at 0.5m distance from floor level if treatment room is located under premises that has protection;

– at 2 m distance from floor level if treatment room is located over premises that has protection.

By using calculated values of damping (K) from table 8, taking into account anode current on X-ray tube, leaden equivalents of protection are to be found and used for following calculation of thickness of protection from other materials (see table 9).

Radiation Safety

There are three essential methods used to minimize external exposure to radiation in radiation safety: time, distance, and shielding

Time

Distance

Shielding

Always check the effectiveness of the shielding before starting an experiment.

Radiation Safety for X-ray Units

Analytical X-ray machines produce intense beams of ionizing radiation that are used for diffraction and fluorescence studies. As stated earlier, X-rays can be characteristic (especially from K shell emission of the target material) or continuous (also called bremsstrahlung). X-ray machines may be hazardous because of their potential for producing high radiation fields. Special attention should be paid to the central beam but secondary emissions from samples, shielding materials and fluorescent screens should also be considered.

The shielding, safety equipment, and safety procedures prescribed for X-ray diffraction equipment are applicable only for up to 75 kV-peak X-rays. Additional precautions are necessary for machines operating at higher voltage (such as interlock systems). The supervisor is responsible for providing a safe working environment by ensuring that all equipment is operationally safe and that users understand safety and operating procedures.

Do not put any part of the body into the X-ray beam. Use safety glasses or prescription glasses to protect eyes from secondary exposure (glasses can not protect eyes from direct exposure).

http://www.ehs.utoronto.ca/services/radiation/radtraining/module0.htm

Biological Effects of Radiation

Can lead to: OR

Radiation Detection and Measurements

1. Check first if the right method (direct or indirect monitoring) is required for the type of radionuclide used.

3. Measure the background before reading the values in the work area.

4. Subtract the background after taking readings in the work area.

5. With the remaining number and the instrument’s efficiency for that particular radionuclide (see sticker), estimate the level of contamination.

6. Take the necessary actions to reduce the contamination below the set limits.

The second method for measuring external dose is personal dosimetry.

This consists of whole body Thermoluminescent Dosimeters (TLDs), extremity TLDs, and neutron dosimeters. The TLDs are contracted with a licensed company and the dose is measured every three months. The results are reported to the UTRPS and to the Health Canada. After checking each report and comparing it to the administrative action levels, the UTRPS sends the results to the workers. These dose measurement results are strictly confidential.

With respect to internal dosimetry, U of T performs two types of bioassays. A baseline measurement for each person starting the usage of sufficiently large quantities of radioactive Iodine, Tritium, or other radionuclides is performed before starting the work. This measurement is important as a reference, but will not be used as a substitute for background of our measurements.

The first type of bioassay is dedicated to Iodine users (I-131 and I-125) and consists of measuring the concentration of radioactive Iodine in the thyroid. This measurement must be performed shortly after the time of use, but not later than 4 days post-usage.

The second type of bioassay is urinalysis. Because most radionuclides used at U of T can be detected in body fluids, this is a very good method to check for possible ingestion or inhalation of various radionuclides. Urinalysis is performed shortly after usage of radionuclides, but no later than 4 days post-usage. If radionuclides are discovered in someone’s body, an estimate of the inhaled or ingested quantity is performed, and compared with the annual Allowable Limit on Intake (ALI) for that particular radionuclide. Immediate action is taken to stop the intake by analysing the work practices, changing the work procedures, etc.

Regulatory Requirements

As stated earlier, the possession, storage, use and disposal of radioactive materials is highly regulated at the international, federal, provincial, municipal, and local (U of T) levels.

U of T Policy, Standards and Procedures for Radiation Safety

A number of radiation safety policies have been developed and adopted by the UTRPA.

Training is considered the first important step in radiation safety. All radioisotope users must have either U of T radiation safety training or equivalent, which must be recognised by the RPS. One-hour administrative training is required for all users, including those with equivalent radiation training. When applying for a new user’s TLD, the permit holder must sign the application and send it to the RPS. A Radiation Safety Officer will check if the new radioisotope user was trained or will contact the new user to arrange for radiation training. At the end of the course, the applicant must pass a written examination. Upon successful completion of the course and examination, a Radiation Safety Officer will administer a short oral quiz in the laboratory where the radioisotope work is being conducted, before providing a radiation course certificate.

A comprehensive set of procedures and standards for radiation safety has been developed and maintained by the RPS. There are procedures for ordering, receiving and transferring of radioactive materials , both from outside and within U of T. Special procedures have also been developed for the disposal of radioactive materials .

Procedures for working with radioactive materials are developed for each particular use by the permit holder. These are audited by the RPS. Special evaluation of the procedures will be performed:

When an external exposure above the administrative action limit is recorded
When an intake is discovered during bioassay
In the case of a self-declared pregnant worker

Procedures and checklists are established for commissioning a new radioactive laboratory. Laboratories are classified as basic, intermediate or high depending on the amount and type of radioactive materials to be used. During commissioning, radiation signs and labels are posted inside the laboratory. Depending on the type of laboratory, special security may be required. Radioactive materials should always be kept locked to prevent access by unauthorised persons. Strict record keeping of received, stored, used, and disposed radioactive materials , as well as contamination monitoring , is also required. These records must be available for the last three years of radioactive use in the laboratory.

To prevent any accidental ingestion of radioactive materials, food and beverages are strictly prohibited inside the radioactive laboratories. After performing experiments with radioactive materials, contamination monitoring must be performed by each user. Results of the monitoring must be recorded and made available to the RPS Radiation Safety Officer and/or CNSC inspectors.

A special procedure is required for checking sealed sources with activities greater than 1mCi (37 MBq). Also, decommissioning of radioactive labs or instruments with radioactive sources is performed according to special procedures.

U of T Radiation Emergency Procedures

During the course of normal operations with radioactive materials, a spill can occur resulting in contamination of personnel or lab equipment and areas. Also, external irradiation can be encountered from a strong gamma or neutron source left unshielded. Appropriate actions must be taken during such incidents to prevent unnecessary doses to personnel and further spread of contamination.

In case of serious injury, medical attention takes precedence over radiological or other concerns. Dial 416-978-2374 or the Campus Police immediately and inform U of T RPS or Campus Police about the incident, injury, and that radioactive materials are involved. Alert everyone in the area and take all reasonable precautions to limit the spread of radioactive contamination or further exposures. Never risk external or internal contamination to save equipment or an experiment.

In case of a radioactive spill, contact RPS immediately if internal irradiation (inhalation/ingestion of radioactive material) is suspected, if excessive external dose is suspected, if significant contamination of personnel is suspected, or in the case of contamination of large areas. In this case, besides the general emergency procedures listed above follow the radioactive spill instructions.

In any clean-up of a radioactive spill, always clean the area until measurements indicate that the contamination is below the contamination limits before removing radioactive warning signs. If there is any questions of the effectiveness of the spill clean up, contact the RPS or U of T Campus Police.

In case of an emergency involving strong gamma or neutron sources, evacuate the area and contact the U of T RPS or Campus Police. Determine the limits of the area with dose rates above 2.5 mSv/hr (0.25 mrem/hr). Restrict access to that area by using radioactive signs and/or tape, closing the doors, etc. Guard the area until RPS/U of T Police representatives arrive.

In case of emergencies involving radiation-producing machines (X-ray), turn off the machine and unplug or shut off the circuit breaker for the machine. In the case of injury to personnel, call 416-978-2374 or the U of T Campus Police, notify the laboratory supervisor, and record all information about the incident (eg. operating voltage and current, exposure time, distance from radiation source).

Radiation protection and patient dose

Both ionizing and non-ionizing radiation as well as ultrasound are used in medical imaging methods. Somatic (occurs in own tissues) or genetic (in descendants) damage in patients or personnel are always a risk of examinations which employ ionizing radiation. Photons of non-ionization radiation (radio wave radiation in a strong magnetic field), as well as ultrasound, carry insufficient energy to cause injuries at diagnostic energy levels. Consequently, radiation protection is needed in practice only in X-ray and isotope examinations and in radiotherapy.

There are many factors which influence image quality. By increasing the amount of radiation (and patient dose) image quality can be increased to a certain level, but simultaneously several factors in the imaging chain can diminish quality. The quality control of imaging methods should be arranged such that high image quality with a dose as low as reasonably achievable (ALARA) is maintained.

The purpose of radiation protection is to eliminate the acute toxicity of radiation exposure and diminish the somatic and genetic risks to patients and personnel. It is useful to remember that the natural background radiation in the Nordic Countries varies between 3-6 mSv (300-600 mrem) per year. There is radiation coming from space, soil (radon gas is a very considerable source of radiation) and construction materials, as well as from our own tissues. Background radiation can vary depending on residential area, life style, etc. This value of 3-6 mSv is the same order as the skin dose from an X-ray image of the body.

Quantities and units of radiation dose

Interactions of X-ray and gamma photons always set electrons in motion with sufficient energy to ionize and excite atoms and molecules. An electron therefore deposits energy in its wake. Around 10-100 ionizations/ m caused by an electron are generated at diagnostic X-ray energies (approximately 33 eV/ion pair). The concept of linear energy transfer, LET (unit keV/ m) can be used to describe this phenomenon together with the concept quality factor Q, explained later. In addition, part of the energy of the electron is absorbed by secondary electrons, so-called delta particles; they in turn have sufficient energy to cause new ionizations.

Exposure

Exposure implies that ions are generated in air as a consequence of the passage of radiation. Ions can be measured with an ionization chamber, which is an air space between two conducting plates coupled to the positive and negative poles of a voltage source. The exposure = the number of ions with negative (or positive) charges divided by the mass of air in the ionization chamber. The SI-unit is C/kg (C = coulomb). The older unit is roentgen R = 2,58 10-4 C/kg.

Absorbed dose

This quantity is the energy per unit mass, which matter has absorbed from radiation. The SI-unit is the gray Gy = J/kg (the old unit was rad = 0.01 Gy). At X-ray and isotope imaging energies (15-500 keV) one R exposure causes approximately 10 mGy (one rad) absorbed dose in all other tissues except in bone, where the absorbed dose at low energies (around 20 keV) reaches up to around 40 mGy.

Kerma

The concept kerma comes from the words Kinetic Energy Released in Matter. It takes into account the dose generated by the aforementioned delta electrons. It is approximately equal to the absorbed dose in air at diagnostic X-ray energies.

Dose equivalent

When energy has been absorbed in tissue the biological effect varies depending on the organ in question, the type of radiation and energy, dose rate, exposure time etc. These are incorporated in the concept quality factor Q, by which the absorbed dose must be multiplied to get the equivalent dose. Its unit is sievert Sv = J/kg (= 100 rem, the old unit).

In X-ray and isotope imaging, Q is approximately 1, because X and gamma radiation deposit relatively small amounts of energy in tissue. Another concept, effective dose, describes the probability of damage to different organs with a weighting coefficient, which is high for radiation sensitive organs such as gonads, bone marrow, lungs, colon, breast etc. and small for other tissues, e.g. muscle. The sum of the weighting factors equals to 1.

From the foregoing it is clear that in diagnostic imaging, the units Gy and Sv, as well as R, rad and rem, have about the same numeric values, although the concepts have different meanings.

Dose rate

One useful concept in dosimetry is the rate, with which a given amount of radiation strikes tissues, for instance kerma rate and exposure rate mR/min, R/h etc. Activity (see the chapter Radioisotopes and radio pharmaceuticals) is also a concept which incorporates the function of time. Whether X-rays from an X-ray device or gamma radiation from radionuclides are discussed, the same concepts can be used to describe radiation phenomena and the biological effects of radiation.

Radiation biology

Ionization and excitation result in fragmentation of molecular bonds with potentially harmful consequences to cell structure, metabolism and organ function. Injuries are divided into genetic and somatic ones. The former can appear in descendants after a long time has elapsed, and the latter may occur quickly (acute consequences) or after a considerable delay. In the peaceful usage of ionizing radiation acute toxicity does not occur.

A distinction is also made between stochastic and non-stochastic effects of radiation. Stochastic implies that even a single “hit” of radiation to one cell or to a small cell group can cause a biological consequence. Damage may be either hereditary (in gonads) or carcinogenic (in tissue). There is no threshold, i.e. the extent of the damage does not depend on absorbed dose (cancer is contracted or not), although the probability of an adverse event increases with dose. This stochastic nature of radiation is therefore the basis of conservative radiation protection.

The non-stochastic effect of radiation has a definite threshold (normally different for every tissue and organ). These have been found from past experience, e.g. in cancer treatment withradiotherapy

during this century. Diagnostic radiation examinations (where skin dose varies between 0.1 mSv and 0.1 Sv / examination) expose the patient to very small doses so the consequences of non-stochastic effects do not evolve. One clear exception is the dose to a fetus, particularly during the sensitive period of organogenesis. Therefore, the indications for pediatric examinations involving ionizing radiation must be examined particularly closely.

It is estimated that if 200 000-2 000 000 people get a dose of l mSv (the same as the background dose per year without radon) it is probable that one person will develop cancer. It is, however, impossible to separate so few cases from cancers caused by other factors, such as environmental toxins and unknown reasons etc.

Many other factors such as the type of radiation and energy, LET value, dose rate, time between exposures or fractionation of dose, different sensitivity of tissues for radiation, biological variations etc. have a significant effect on the likelihood of injury.